System Fields Behavior not working

[Alvin]

Hi Community, I am trying to show/hide and make fields required using behavior within System Fields (Priority, Resolution) but even the sample in Scriptrunner Behavior is not working but it throws no errors. Can you please help me

import com.atlassian.jira.issue.resolution.Resolution

def resolutionField = getFieldById("resolution")

def fixVersionsField = getFieldById("fixVersions")

def resolution = resolutionField.getValue() as Resolution

if (resolution.name == "Fixed") {

fixVersionsField.setRequired(true)

fixVersionsField.setHidden(false)

} else {

fixVersionsField.setRequired(false)

fixVersionsField.setHidden(true) }

it just not follow the behavior. 

[Alvin]

Already fixed, sometimes it is just not working. I dont know if its a bug or something